Biology · Environmental Studies

Microbiology and Nitrogen Cycle

950 Questions

This hub focuses on microbiology and the nitrogen cycle, covering essential concepts about bacteria and soil microbes. Topics include nitrogen fixation, bacterial structures, and soil microbial processes. These concepts are frequently tested in general science sections of various competitive exams.

Nitrogen fixing bacteriaGram-positive bacteriaBacterial flagellaDenitrifying bacteriaAmmonia conversion processBacterial resting spores

Microbiology and Nitrogen Cycle Questions

Multiple choice

The bacteria that cause botulism are

  1. facultative anaerobes

  2. obligate aerobes

  3. facultative aerobes

  4. obligate anaerobes
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Clostridium botulinum, the bacterium that causes botulism, is an obligate anaerobe meaning it requires an oxygen-free environment to grow. It cannot survive in the presence of oxygen, unlike facultative anaerobes which can adapt to both conditions.

Multiple choice

Which of the following options has Acid Fast organisms?

  1. Staphylococcus, Streptococcus, Clostridium and Nocardia

  2. Cryptospordium parvum, isospora, cyclospora cysts

  3. Enterobacteriaceae, vibrio cholera, pseudomonas aeruginosa, mycobacterium leprae

  4. Legionella micdadei, nocardia, head of sperm

  5. Both (2) and (4)
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Correct answer because option numbers (2) and (4) both have groups of acid fast organisms.

Multiple choice

Organisms that fix nitrogen in aquatic habitats are

  1. diatoms

  2. protozoans

  3. desmids

  4. cyanobacteria
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cyanobacteria, also known as blue-green algae, are the primary organisms responsible for nitrogen fixation in aquatic habitats. They possess specialized cells called heterocysts to convert atmospheric nitrogen into usable forms.

Multiple choice

Which one of the following statements is correct?

  1. Legumes fix nitrogen only through specialized bacteria that live in their leaves.

  2. Legumes fix nitrogen independent of any specialized association.

  3. Legumes fix nitrogen only through the specialised bacteria that live in their roots.

  4. Legumes are incapable of fixing nitrogen.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Leguminous plants have a symbiotic relationship with nitrogen-fixing bacteria, most notably Rhizobium. These bacteria reside in specialized nodules formed on the roots of the plant, converting atmospheric nitrogen into a form the plant can absorb.

Multiple choice

The bulk of nitrogen in nature is fixed by

  1. chemical industries

  2. symbiotic bacteria

  3. lightning discharge

  4. denitrifying bacteria
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biological nitrogen fixation, particularly by symbiotic bacteria like Rhizobium in legume nodules, accounts for the vast majority of nitrogen fixed in nature. This process far exceeds the amounts fixed by lightning or industrial processes.

Multiple choice

A bulk of nitrogen in nature is fixed by

  1. lightning discharge

  2. denitrifying bacteria

  3. symbiotic bacteria

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 Rhizobium is the most commom symbiotic bacteria, which carry out the nitrogen fixation.

Multiple choice

Bacteria cannot survive in a highly salted pickle because

  1. salt inhibits chemosynthesis

  2. bacteria do not have enough light for photosynthesis

  3. bacteria become plasmolysed and are consequently killed

  4. the pickle does not contain nutrients necessary for bacteria to live in
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Due to the hypertonic nature of salt. Any living cell in such an environment will become plasmolysed (loss of water) and die or become temporarily inactivated.

Multiple choice

Aerotolerant anaerobes in culture media are

  1. the bacteria which have anaerobic growth, but continues in the presence of oxygen

  2. the bacteria which have only aerobic growth and oxygen required

  3. the bacteria which have both aerobic and anaerobic growth, and have greater growth in the presence of oxygen

  4. the bacteria which have only anaerobic growth, but ceases in the presence of oxygen

  5. the bacteria which have only aerobic growth, but oxygen is required in low concentration
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aerotolerant anaerobes: Bacteria, which have anaerobic growth, but continues in the presence of oxygen.

Multiple choice

Which of the following components chemically remove molecular oxygen that might interfere with the growth of anaerobes in a growth media?

  1. Seaweed extract (polysaccharide)

  2. Biotin

  3. Sodium Thioglycolate

  4. Oxyrase

  5. Both the options 3 and 4
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

 
Sodium Thioglycolate combines with dissolved O2 to deplete O2 in media.Oxyrase is a bacterial respiratory enzyme that can be put in media; it combines O2 with H+ to remove O2 by forming H2O and turns the petri dish into a mini-anaerobic chamber.

Multiple choice

To which family does nitrogen fixing bacteria present in plants belong?

  1. Malvaceae

  2. Cruciferae

  3. Leguminosae

  4. Papaveraceae
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Nitrogen-fixing bacteria like Rhizobium form symbiotic relationships with the root nodules of plants in the Leguminosae family, which includes peas and beans. These bacteria convert atmospheric nitrogen into a form that plants can use for growth. Other families like Malvaceae or Cruciferae do not typically host these specific symbiotic bacteria.